Cleanup: Pass std::string as const reference if possible

chrome/browser/safe_browsing/client_side_model_loader.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/safe_browsing/client_side_model_loader.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 75 matching lines @@
     : name_(FillInModelName(is_extended_reporting, GetModelNumber())),
       url_(kClientModelUrlPrefix + name_),
       update_renderers_callback_(update_renderers_callback),
       request_context_getter_(request_context_getter),
       weak_factory_(this) {
   DCHECK(url_.is_valid());
 }
 
 // For testing only
 ModelLoader::ModelLoader(base::Closure update_renderers_callback,
-                         const std::string model_name)
+                         const std::string& model_name)
     : name_(model_name),
       url_(kClientModelUrlPrefix + name_),
       update_renderers_callback_(update_renderers_callback),
       request_context_getter_(NULL),
       weak_factory_(this) {
   DCHECK(url_.is_valid());
 }
 
 ModelLoader::~ModelLoader() {
 }
@@ skipping 91 matching lines @@
 }
 
 void ModelLoader::CancelFetcher() {
   // Invalidate any scheduled request.
   weak_factory_.InvalidateWeakPtrs();
   // Cancel any request in progress.
   fetcher_.reset();
 }
 
 }  // namespace safe_browsing